1. Field of the Invention
The present invention relates to an all-terrain vehicle with a speed sensing device. Moreover, the present invention relates to an all-terrain vehicle with a gear transmission.
2. Description of the Related Art
Construction of a four-wheeled all-terrain vehicle and a power train for the four-wheeled all-terrain vehicle will be briefly described. The four-wheeled all-terrain vehicle has a body frame, a pair of front wheels and a pair of rear wheels supported on the body frame, an engine mounted on a part of the body frame between the front and the rear wheels, and steps disposed on the right and the left side of the engine, respectively. A handlebar is supported on an upper part of the body frame, and a straddle-type seat is disposed behind the handlebar. A speed meter (speed indicating device) is held on a middle part of the handlebar. Levers including a brake lever are disposed near the grips of the handlebar.
A crankcase of the engine extends rearward, and a transmission case is joined to the rear end of the crankcase. A gear transmission is built in the transmission case. A variable-speed V-belt drive is disposed on the right side of the crankcase. The output power of the engine is transmitted through the variable-speed V-belt drive to the gear transmission.
A drive shaft is extended in the back-and-forth direction under the transmission case. The drive shaft has a front end connected to a front propeller shaft, and a rear end connected to a rear propeller shaft. The front propeller shaft has a front end part interlocked with a front reduction gear built in a front reduction gear case. The rear propeller shaft has a rear end part interlocked with a rear reduction gear built in a rear reduction gear case.
In the four-wheeled all-terrain vehicle of this type, a conventional speed sensor is placed in a rear axle supporting part of the rear reduction gear case (axle case) and measures the rotation of a rear axle.
Mechanical speed sensors and electric speed sensors are available as a speed sensor of a vehicle. The mechanical speed sensor has a cable or a rod, a gear attached to the cable or the rod and engaged with a gear attached to a rotating member. The cable or the rod, and the gear attached to the same serve as a speed signal transmitting mechanism. The electric speed sensing device has a rotor connected to a rotating member, converts the rotation of the rotor into a corresponding electric pulse signal, and gives the electric pulse signal through a signal line to the speed indicating device.
Referring to FIG. 8 showing a related art speed sensing device disclosed in JP-A 183499/1999 for a vehicle, the speed sensing device 500 is attached to a right side wall of a rear reduction gear case 522 included in an all-terrain vehicle. The speed sensing device 500 has a screw gear 501 supported coaxially with a rear axle 522a for rotation together with the rear axle 522a, a pinion 503 supported for rotation and engaged with the screw gear 501. The rotation of the pinion 503 is measured and a speed signal corresponding to the rotating speed of the pinion 503 is sent through a harness 510 to a speed meter.
When the speed sensing device 500 is attached to the rear reduction gear case 522 as shown in FIG. 8, the speed sensing device 500 is splashed with mud and water while the vehicle is traveling. Since the speed sensing device 500 is distant from the speed meter disposed in a front part of the body frame of the vehicle, and the harness 510 is long, much time and great effort for wiring are required, and the harness 510 must be protected with a cover.
A conventional gear transmission for an all-terrain vehicle includes a chain transmission mechanism as a reversing transmission mechanism interposed between a transmission input shaft and a counter shaft. As shown in FIG. 9, a transmission input shaft 402 connected to a driven shaft 401 included in a variable-speed V-belt drive, a counter shaft (intermediate shaft) 403 and a transmission output shaft 404 are extended in parallel to each other and are supported in a transmission case 400. A forward high-seed gear 405, a forward low-speed gear 406 and a small reverse sprocket 407 are mounted on the transmission input shaft 402. Forward intermediate gears 410 and 411 respectively engaged with the forward gears 405 and 406, an intermediate output gear 413 and a large reverse sprocket 412 are mounted on the counter shaft 403. A chain 415 is extended between the sprockets 407 and 412. An output gear 416 engaged with the intermediate output gear 413, and a bevel gear 422 engaged with a bevel gear 421 mounted on a drive shaft 420 are mounted on the output shaft 404.
A shift dog clutch has a first shift sleeve 425 and a second shift sleeve 426 mounted on the counter shaft 403. The first shift sleeve 425 is interposed between the reverse sprocket 412 and the forward high-speed intermediate gear 410. The second shift sleeve 426 is disposed near the forward low-speed intermediate gear 411.
A shift rod 430 is provided with a first shift arm 431A and a second shift arm 431B respectively engaged with the shift sleeves 425 and 426.
When setting the gear transmission shown in FIG. 9 for a forward high speed or a reverse, the first shift sleeve 425 is shifted. On the other hand, when setting the gear transmission for a forward low speed, the second shift sleeve 426 is shifted. Techniques relating to the present invention are disclosed in JP-A 106162/1987.
Another known gear transmission is not provided with any chain transmission mechanism like that mentioned above, and is provided with a transmission input shaft, a counter shaft and a reverse idle shaft disposed between the transmission input shaft and the counter shaft, and drives an output shaft in the reverse direction by a gear for going backward.
However, those conventional gear transmissions for all-terrain vehicles have the following problems.
(1) Although the gear transmission shown in FIG. 9 including the chain transmission mechanism as a reversing transmission mechanism does not need a reversing idle shaft as an intermediate shaft, the transmission case 400 must be wide because the chain 415 must be a wide one to transmit a large torque, and the chain transmission mechanism requires much assembling work.
(2) In some cases, the chain transmission mechanism needs a tensioner to prevent the generation of rattling noise due to the elongation of the chain 415.
(3) The gear transmission provided with the reverse idle shaft as an intermediate shaft and not provided with any chain transmission needs an additional shaft and hence the transmission case is large and the gear transmission has complicated construction.